Coronavirus is the cause of many common colds in humans. Recently, infection in humans with a new coronavirus led to a worldwide outbreak of an acute respiratory disease, i.e., severe acute respiratory syndrome. See, e.g., Ksiazek et al., N. Engl. J. Med., 2004, 348: 1953-1966. The first severe acute respiratory syndrome case was identified in Guangdong, China in November, 2002. The disease later spread to more than 25 countries. By Jul. 31, 2003, about 8,100 severe acute respiratory syndrome cases and about 800 severe acute respiratory syndrome-related deaths were reported around the world.
Various drugs have been investigated for use in treating severe acute respiratory syndrome. They include ribavirin, corticosteroids, Kaletra, glycyrrhizin, and certain human interferons. See, e.g., Peris et al., Lancet, 2003, 361:1319; Cinatl et al., Lancet, 2003, 361:2045; and Cinatl et al., Lancet, 2003, 362:293. However, these drugs require high dosages to exert efficacy. Thus, there exists a need to identify compounds that can more effectively treat severe acute respiratory syndrome.